The quality of cancer registry data is of great importance to the usefulness of a cancer registry. To investigate the quality of its data the IKL cancer registry (Integraal Kankercentrum Limburg) performed a study with the aim of comparing data supplied by clinicians with data collected by registration personnel. Twenty clinicians reabstracted the information of a random sample of about ten of their patients, who were diagnosed with cancer in 1989 or 1990. After coding, the information was compared with the contents of the cancer registry records. For comparison of agreement the information of 190 cases was available. The relative frequency of major disagreements was 0% for date of birth, 0% for gender, 5% for date of incidence, 6% for primary site, 2% for laterality, 2% for histologic type and 2% for behaviour code. In general, the disagreements could be attributed to the handling of different coding rules (incidence date), or to a lower level of precision by the clinician in comparison to registration personnel (primary site, laterality). This study has shown that registration personnel are able to collect data with a high degree of accuracy.